The present invention relates to the field of agriculture and more particularly, relates to a method of treating soil.
The treatment of soil for agriculture purposes is done for many different purposes. Thus, a soil treatment can include the application of many different agents for various purposes ranging from the addition of fertilizers to treating the soil to remove pathogens as well as to increase soil bacteria populations. The control of pathogens in the soil is an issue which has always been of importance and has increasingly become of greater importance due to current methods employed. Thus, the most widely accepted means of treating soil is the use of methyl bromide. However, methyl bromide has been recognized as an ozone depleting chemical and as such, International Agreement has stated that all production in developed countries must be phased out by the year 2005.
Alternatives to methyl bromide do not readily exist and this poses a substantial problem to agricultural producers. Estimates of a cost of over 1 billion dollars annually have been made as a potential future crop damage resulting from the removal of methyl bromide from the market for soil fumigation. Many agriculture products widely produced on a large scale such as potatoes, tomatoes, peppers; strawberries, etc. are susceptible to soil borne pathogens.
Other products for treating soil do exist but have not gained wide acceptance. There are also natural methods for treating the soil including crop rotation and field fallowing. However, these approaches provide a substantially lower return to the agricultural user.
It is therefore an object of the present invention to provide a method for the treatment of soil which is effective to control some bacterial and fungal soil pathogens.
According to one aspect of the present invention, a method is provided for reducing bacterial and flail soil pathogens comprising the step of applying to a locus to be treated a chemically effective amount of a lignosulfonate.
In a flier aspect of the present invention, there is provided a method of enhancing the characteristics of a soil having bacterial and fungal pathogens therein, the method comprising the steps of mixing ammonium lignosulfonate, at least one agriculturally desirable microorganism, and a food material for the microorganisms, allowing the microorganisms to multiply for a period of time sufficient for the microorganisms to have a concentration of at least one hundred million bacteria per milliliter, and subsequently applying to the soil a chemically effective amount of the mixture.
In a further aspect of the present invention, there is provided a method of treating potato scab disease caused by bacteria Streptomyces comprising the step of applying to a soil containing the bacteria Streptomyces ammonium lignosulfonate in an amount of between 0.05% and 5% on a volume/weight basis and incorporating the ammonium lignosulfonate in the soil.
In a further aspect of the present invention, there is provided a method of controlling at least one soil pathogen selected from the group comprising Verticillium dahliae, Streptomyces, Phylophthora, Pythium, Rhizoctonia and Sclerotinia comprising the step of applying to a locus containing one of the soil pathogens a chemically effective amount of a lignosulfonate.
Lignins are a natural polymer which are generally produced as a co product of the paper industry, the lignins being separated from the trees by a chemical pulping process. Lignosulfonates (also known as lignin sulfonates and sulfite lignins) are products of sulfite pulping. Other delignifying technologies can use an organic solvent or high pressure steam treatment to remove lignins from plants.
As aforementioned, lignin is a very complex natural polymer, the exact chemical structure not being known. The physical and chemical properties may differ somewhat depending on the extraction technology. Lignosulfonates have typically been used for their dispersing, binding, complexing and emulsifying properties. Lignins have been used for many years and extensive studies have been done to test lignin impact on the environment To date, lignins have been shown to be safe and not harmful to plants, animals and aquatic life when properly manufactured and applied.
Toxicological studies of lignosulfonates using laboratory animals have been conducted at Stanford Research Institute International in California. Lignosulfonates were found to be essentially non-toxic and non-irritating, not mutagenic or genotoxic and can be safely used in animal and human food contact products. Lignosulfonates have been approved for use as constituent in animal feed and various food contact materials and pesticide formulations by the U.S. Food and Drug Administration.
Lignosulfonates have also found use in various compositions used for gels and binders. Thus, lignosulfonates have been proposed as one component of various binding compositions and particularly suitable for the plugging of wells and the like. It is also been suggested in the art that they can be used in combination with other compounds, as a dust control composition for the treatment of fertilizers.
Calcium lignosulfonate has also been shown as suitable for controlling nematodes which are of the animal kingdom. Reference may be had to U.S. Pat. No. 5,696,094 which shows that various nematode species are affected by the use of calcium lignosulfonate. However, there is no teaching therein that soil borne bacterial and fungal pathogens are affected.
It is also known from Chem. Abstr., vol. 88, no. 7, 13 Feb. 1978 Columbus, Ohio, US; abstract no. 49520, LICHKO, R. P. ET AL that the application of ammonium lignosulfonates increase the calcium ion content in certain soils.
It is known from German Patent DE-A44 04 860 that lignosulfonates can be applied to the soil and/or leaves of a plant.
It is also known from Database CROPU Derwent Izfoimation Ltd. Abstract number, 92-85525, A. Khakimov, R. Teshabaeva and R. Sayrsakova that lignin may be used as a substrate for introducing bacteria before sowing cotton.
It has surprisingly been found that lignosulfonates are useful for controlling both bacterial and fungal soil borne pathogens and in addition, by themselves or in combination with other materials, can be useful as a delivery agent for other microorganisms known to be useful for agricultural production.
The mechanism by which soil borne bacterial and fungal pathogens are controlled by lignosulfonates is not understood However, tests have shown that the application of lignosulfonates to a soil medium can have extremely beneficial results.
As a readily commercially available product, reference herein will be made to ammonium lignosulfate with it being understood that other lignosulfonates may be utilized, either alone or in combination.
The concentration of the ammonium lignosulfonate to be applied to the soil may vary. The determination of the amount can be ascertained by one skilled in the art and which amount may vary depending on different parameters. These parameters could include the type of soil, the crop to be grown, any specific bacterial or fungal pathogen to be controlled, time of application, etc. Thus, for example, depending upon the type of crop to be grown and the time when the crop is placed in the soil, the question of phytotoxicity to the crop may or may not be of concern. One could apply a relatively high dosage when the soil will not be planted for a period of time or alternatively, one could utilize a series of applications at relatively low dosages to provide a cumulative effect over a period of time. Generally, an amount of between 0.05% and 5% on a volume/weight basis (product/soil) may be utilized and when it is applied in a single application, it is preferably applied at a volume/weight basis of between 0.1% and 2%.
As mentioned above, the amount of lignosulfonate to be applied will depend upon the specific application. In the preferred embodiments, an amount of at least 0.1% by volume would be employed given that the material is available as a 45% solution (45% solid/55% liquid). The amount would naturally depend on the bacterial and fungal pathogens to be controlled, the economics, etc. In certain instances and as will be seen hereinbelow, ammonium lignosulfonate might have a biocidal impactxe2x80x94i.e. its effectiveness initially increases with increasing amounts and then subsequently decreases and then increases once again. This bimodal impact phenomenon has been reviewed by Schatz, A. Schalscha, E. B. and Schatz, V, 1964. xe2x80x9cSoil organic matter as a natural chelating material. Part 2: The occurrence and importance of paradoxical concentration effects in biological systemsxe2x80x9d. Compost Science 5:126-130.
The method of application of the ammonium lignosulfonate to the soil may be selected from any suitable including application as a dust or granular material or application by means of a liquid medium such as water, etc. Generally, a water based application would be preferred.
The ammonium lignosulfonate may be used either alone or in combination with other materials, including biological and chemical pest protectants. In one particularly preferred embodiment, the ammonium lignosulfonate may also be employed as a delivery agent for microorganisms identified to be useful for agricultural production. The benefits of these microorganisms may be as biofertilizers or as biological control agents. A number of such microorganisms are known in the art and could be incorporated in a mixture of the ammonium lignosulfonate and any additional materials. Such microorganisms would include bacteria, including the gram positive Streptomnyces, fungi, algae, and nematodes that attack insect pests. Commonly employed organisms include, Agrobacterium spp., Pseudomonas spp., Bacillus spp., Rhizobium spp., Streptomyces spp., Azospinilum spp., Enterobacter spp., Trichoderma spp., Gliocladium spp., Sporodesmium spp., Pythium spp., Fusarium spp., Verticillium spp., Talaromyces spp., various wood decomposing fingi, etc.
One particular advantageous method comprises combining ammonium lignosulfonate with desired microorganisms and food for the microorganisms and then allowing the microorganisms to grow in the ammonium lignosulfonate for a period of time sufficient to substantially increase in numbersxe2x80x94i.e., at least one billion bacteria per milliliter of mixture. Such a method provides an extremely economical means of delivering the microorganisms to the soil as the mixture can be then diluted to apply one million bacteria per milliliter of water applied to the soil.
A further advantage of the use of a lignosulfonate is the restoration of the soil with the lignins from the lignosulfonate. Thus, many soils have, over a period of years, become depleted of many of the natural elements which were originally present in the soil. The application of the lignins, being a plant material, can act to restore such elements and increase soil health.
Ammonium lignosulfonate has been used in feed products. In particular, one such product is marketed under the trademark xe2x80x9cEarth Alivexe2x80x9d and is intended for use on house plants. The product contains fertilizer, ammonium lignosulfonate and certain bacteria. This product was tested in conjunction with tests on ammonium lignosulfonate without the additives.